Eange findee



. (No Model.) 3 SheetsSheet 1.

-B. A, FISKE.

RANGE FINDER. No. 406,829. Patented July 9, 1889.

ATTORNEY.

25 N. PETERS. Phnla-Lilhogmphm Wuhmglon, ac,

(No Model.) 3 Sheets-Sheet 2.

B. A. FISKE. RANGE FINDER.

No. 406,829. Patented July 1889.

ATTORNEY,

3 Sheets-Sheet-3. B. A. FISKE. RANGE FINDER.

(NoModeL) No. 406,829. Patented July 9,1889.

7 llVl/E/VTUR. n Q. 5941!," BY

gWlT/VESSES:

h7g5 ATTO NEY.

N. PETERS. Phoio mhngnph lr. Washington. D. C.

UNITED STATES PATENT OFFICE.

BRADLEY A. FISKE, OF THE UNITED STATES NAVY.

RANGE-FINDER.

SPECIFICATION forming part of Letters Patent No. 406,829, dated July 9, 1889.

Application filed October 17, 1888. Serial No. 288,505. (No model.)

To all whom it may concern: I Be it known that I, BRADLEY A. FISKE, 0 the United States Navy, have invented a new and useful Improvement in Range-Finders,

of which the following is a specification.

My invention consists in a new apparatus for determining the angular change in position of a body moving about a center by measuring the electrical resistance of a conductor extending between the initial and final positions of said body.

The accompanying drawings are (Figure 4-. excepted) all electrical diagrams, not drawn to scale, and symbolically represent my invention. In Fig. 1 is shown a Wheatstone bridge, in one member a of which is arranged an arc and a movable arm traversing the. same. In Fig. 2 is shown a \Vheatstone bridge having arcs and movable arms arranged in two members a b. In Fig. 3 is shown a Wheatstone bridge in which arcs connect adjacent members, as a c and b d, and movable arms sweeping over said ares are connected to the battery. Fig. 4 is a mathemat ical diagram illustrating the method of deter-- mining the angle ATO. Fig. 5 shows a disposition of my range-finder in connection with a galvanometer, and Fig. 6 the same in connec-f tion with a telephone.

Similar letters of reference indicate like parts.

In Fi 1, let a b 0 (Z represent the four members of an ordinary Wheat-stone bridge, and g the transverse member, in which is con-j nected the galvanometer g. A battery f is lso connected to the bridge in the usual way.

,In the members 0 and (Z are placed the fixed resistances c and d, and in the member I) the variable resistance 19' also, as usual. One wire from battery f, however, connects to the end of member 0, and also to the pivot l of a swinging arm 1'. The extremity It of arm 1; moves over and maintains electrical contact with an arc h of conducting material, which has one extremity j connected, as shown, to the member a of the bridge. It is obvious that when the arm 2' is in the position shown in full lines in Fig. 1 then the current will traverse the whole are h, and when said arm is in the position indicated by dotted lines, Fig. 1, then the are It will be cut out and the current will pass directly to member a. Now

assume the arc 7L to be made of such material and so proportioned that its electrical resistance to a current traversing it will be proportional to the length of are included between the contact end 70 of arm 11 and the connecting-pointj of member a with said are. Therefore the resistance interposed in the member a of the bridge will be commensurate with the angle j Z k, and if this resistance be known the angle is also known. Let it now be assumed that the galvanometer g and variable resistance 1) be located at some point distant from the moving arm 1', from which said arm is invisible or inaccessible. Clearly, then, an observer stationed at the galvanometer g and resistance 19 can, by noting the galvanometer and adjusting the resistance in the usual way, determine the resistance equili- 7o brating any position of arm 2' along the are h, and so discover the angle of adjustment of said arm; or, having adjusted the resistance 1) at some given figure, the observer may, by simply noting the galvanometer or any other suitable indicating device, visual or audible, determine when the arm i is placed at a desired angle corresponding to the adjusted resistance, and this indicating device may obviously be at the place where the moving arm is located, so that the operator there may thus know when he has placed the arm at the predetermined point or at the distant station, so that the operator in charge of the resistance b may know that the arm has been adjusted properly; or two indicating devices in the same circuit may give warning to both operators, as above, simultaneously.

Various practical applications of this apparatus will readily suggest themselves to those skilled in the art. Thus, for example, the elevation or training of a gun may thus be determined or recognized from a distant point, the longitudinal axis of the gun corresponding to the arm 1'.

Referring now to Fig. 2, it will be apparent that in lieu of the variable resistance 1) in the member I) there is arranged an arc h and swinging arm 2'. The are h is connected at one end j to the member I), and the swin I06 ing arm t" makes contact at one end is with said are, and to its pivot Z is connected the member (Z. The aivangement and construction of are h and arm 2" are similar to that of are 71 and arm Consequently when the arm 1' is set at a certain point onthe are 71 the arm 1" must be set at the corresponding point on the arm 7t, in order that the resistance of the lengths of the arcs h h, respectively, between the point- 71 and point 71 and point It" and point 71 may balance; hence if the arm 70 be set at a certain angle the observer at arm k may recognize that angle by noting the position of the arm 70 and the galvanometer, as before. It will. be observed, however, that the effect of moving the arm 1' over are 71 is practically to lengthen or shorten or to interpose more or less resistance in the member a of the bridge, and by operating the arm 1 a like effect is produced in the member b. The resistances or lengths of the members c and d remain unchanged.

Referring now to Fig. 3, there is shown an arrangement which forms the basis of the specific embodiment of my invention, more particularly hereinafter described. In said Fig. 3 the are his connected at its respective ends j J to the members a c, and the are h is similarly connected at j J to the members I) (Z. The battery-wires connect to the pivots Z Z of the arms 1' 1", as before. Now when the arm 1' is moved from its middle position on its are toward j less resistance is caused in the member a and more resistance in member 0, and when moved in the opposite direction the reverse occurs. So, also, a similar effect is produced by moving arm 1", and thus I may affect the resistance offered by all four members of the bridge, instead of that due to only two of them; and'I' may obtain differential results, as will more fully be apparent in the following description of the application of my invention to a device for measuring distances, such as a range-finder for guns.

Referring to Fig. 4:, let T be the position of the object the distance of which from the point A it is desired to ascertain. Let AB be any short base-line. Draw A at right angles to BT, EA parallel to BT, and prolong AT as to D. By trigonometry AC AT Sill ATC l and j AC=AB Sill ABC, whence AT=AC eosec ATO 5' AT=AB sin ABC cosec ATO.

"5 5 are GH. Arc GH:arc 7'I-larc jG, and are jtI arc 7" K; hence are GH:arcj'KarcjG.

In Fig. 5 the diagrams Figs. 3 and 4 are combined, 1' 1", as before, being swinging arms traversing the ares 71 71, and the connections a b c (l of the bridge being present also, as before. Let the arms 1 and 1" represent alidade-arms or telescopes, both directed upon the object T. The arcsjG and jK not being equal, the bridge will not balance; but when the telescope 1' is moved to the line Ell then the bridge will balance; but the distance thus moved is the arc GH, the length of which may be read off from the are 71 itself. It will be seen, therefore, that the operation of determining the distance AT becomes, by the aid of this apparatus, exceedingly simple. The scales or arcs (L 71' are fixed in place with their zero-points coinciding with the base-line, as shown. The observers at the respective telescopes 1 and 1" direct their lines of sight upon the object. The observer at 1' notes the angle jAG, or length of are G. He then moves the telescope 1' until the galvanometer g, which may be placed conveniently near his position, shows no deflection, and notes the W angle jAH, or length of arcjH. The difference between the arcs 3G and jH equals the are Gll, whence the angle ATE, as already explained. The foregoing arrangement, Fig. 5, involves the determination of the angle ATB, and hence the distanceAT, by the observer at the arm 1', or, in other words, by an observer at the base-line. Iwill now explain the disposition of the apparatus whereby an observer at a point distant from said baseline may at once read off the distance AT from a suitable scale.

Referring to Fig. 6, the members a and b of the bridge are connectedto opposite extremities of a bar 111 T0 of conducting material, and the members a dare connected to the extremities of a similar and parallel bar 0 p. Adjustable upon said bars 0 p and 111 11 is a slider 1 1", having a middle portion 3 of insulating material, so that the current from bar 111 11 for example, does not pass across said slider 1* 1" to bar 0 p, but proceeds by the wire g through the telephone g, which here takes the place of the galvanometer g in the preceding figures. Interposed in the battery-wire, as at t, is any form of automatic circuit-breaker or buzzer, the object of which is to produce an audible sound in the telephone g. Suppose, now, that the telescopes 1' and 1" are sighted upon the distant object T, as before,

and that the slider 1 is at the middle point 1 of the parallel bars 111 11 and 0 p. The resistances in the bridge will obviously not balance, and the sound of the buzzer will be heard in the telephone 9. It has already been explained in connection with Fig. 5 how, by moving telescope 1 to the point H, the resistances might be balanced, and if that were done, with the arrangement shown in Fig. 6, the fact would obviously be indicated by a cessation of sound from the telephone; but, now, let it be assumed that the telescope 1', after being sighted upon the object T, is not moved, or, in other words, that the observers respectively at the two telescopes 1' and 1' simply adjust their instruments in line with T. Obviously, then, the distance on the bridge from 1" to G (member a) is less than the distance from 1" to 7; (member 7)) by the length of the arc Gll. Similarly the distance on the bridge from 1 to G (member 0) is greater than the distance from 1" to 7; (member d) by the length of arc GH.

Now let the resistance per unit length of ICC fixed elevation-for example, eighteen dethe bars on n 0 p be made equal to or with some definite'relation to the resistance per unit length of the arcs h h, and lay off on bar on n a distance r 3 and on bar 0 p a distance r 3, said distances being such that the resistance due thereto will be equal to that of the are Gl-I. Clearly, if the end a" of the slider be moved to the position 2 on bar m n, the member a will be increased and the member I) will be diminished bythe distance r 3, which oiters a resistance equal to one-half that of arc GH, and if the end r of the slider be moved to the position 2 on bar 0 p then the member 0 will be decreased and the member (Z increased by the distance r 2, which also has a resistance equal to one-half of arc GII. As both ends of the slider move simultaneously, it follows that when its extremities are adjusted in the position 2 then the bridge will balance and the sound in the telephone will cease. Applying this practically, let the bars 4n n 0 p be laid o'lt in suitable scale-divisions from r to n and 'L" to 17. The two telescopes i and 91 being sighted on the object, the distant observer listens at the telephone g" and moves the slider r 7' along the bars m n 0 19 until the sound ceases. The scale marked on the bars then shows an indication corresponding to the length of are GH, or, if desired, actual distances corresponding to such indications.

To illustrate'the practical utility of the apparatus, the following instances may be given: The telescopes 1'- z", suitably mounted upon their arcs h h, are given 1.0 two observers, who proceed to a skirmish-line, or to any other advanced position, and, selecting a base-line of predetermined length, train their instruments upon any desired point of an enemys works or column. The fact that this is done may be indicated by any suitable flag-signal, or by one sent electrically to the rear over the bridge-connections. The observer at the telephone 9' may be supposed to be stationedin proximity to a battery of guns ready to open fire. As soon as the signal is sent that the telescopes are sighted the observer at the telephone adjusts the slider r 0' until the sound in the instrument ceases, and then determines the range from the marks on the bars m n 0 p, when the pins are laid accordingly. The invention is, however, especially applicable to use in connection with pneumatic gunsfor the projection of shells charged with high explosives. A gun of this type is placed in the bow of a vessel at a certain grees-and the range of the projectile is regulated by varying the air-supply admitted to the gun. It thus becomes highly important to determine the distance of i the target with all possible accuracy. The two telescopesi 2" may be mounted on opposite sides of the vessels upper deck-her breadth of beam, for example, being the known base-linewhile the telephone 9 may be located below and convenient to the air-regulating valve of the gun. The observers on the upper deck train their telescopes 011 the object, and the observer at the telephone determines the distance in the manner already described, and in accordance with this determination adjusts the valves.

By alidade-arm, as herein used, I mean a bar or arm pivoted at one extremity and provided with sights or other means whereby it may be longitudinally directed, after the manner of a telescope, upon a distant object, and I include in such term a sight-tube, telescope, or like device.

I claim 1. In a range or position finder, in combination with a source of electricity and an indicating device such as described, two similar bodies of conducting material similarly disposed with reference to a predetermined base-line, alidade-arms establishing and maintaining electrical contact with said bodies,

and circnit-connections, as set forth, and including a WVheatstone bridge lnving adjacent members d and 0 connected to said' arms and adjacent members a and 11 connected to corresponding extremities of said bodies.

2. In a range or position finder, in combination with a source of electricity and an indicating device, such as described, two similar bodies of conducting material similarly disposed with reference to a predetermined base-line, alidade-arms establishing and maintaining electrical contact with said bodies, and circuit-comrections, as set forth, and including a Wheatstone bridge having adjacent members, as (Z and c and a and 12, connected to corresponding ends, of said bodies.

8. The combination of the four members a b e (Z of a VVheatstone bridge, two arcs h h, respectively interposed between members a c and l) (1, two pivoted radial arms 6 i, respectively having their free ends moving over and maintaining electrical contact with said arcs, a source of electricity having one pole connected to one of said arms and the other pole connected to the other of said arms, two bars of conducting material respectively interposed between members a b and c d, contact-pieces adjustable upon each of said bars, aloop-conductor connected at its ends, respectively, to said contact-pieces, and an indicating device, such as described, in said loop.

BRADLEY A. FISKE.

Vitnesses:

PARK BENJAMIN, MT. BOSCH. 

